Below, five theories on what could possibly be holding Swiftenhaal together:

1. They're both promoting something. He's baring all in a new movie, "Love and Other Drugs." She's baring her soul in a new album, "Speak Now." In addition to the press they're getting for those projects, they're now having their every move tracked because of their unlikely coupling. PerezHilton.com published the first photo of the couple over the weekend; hundreds of people Tweeted it, thousands gave it the thumbs up on Facebook. Publicity win. (Of course, Swift and Gyllenhaal's publicists have yet to actually say anything -- neither immediately returned ABCNews.com's requests for comment.)

2. She wants a man, he wants a blonde. With four Grammys under her belt and millions of albums sold, Swift has seen success that belies her age. For her, the average 20-year-old, beer-swilling, fist-pumping dude won't cut it. "It's impossible that she would even think or breathe like an average 20-year-old," said psychologist Wendy Lee Walsh. "She's more mature. She may want to showcase that to her public by dating an older man."

As for Gyllenhaal, whose previous paramours include Kirsten Dunst and Reese Witherspoon, his attraction to the flaxen-haired Swift seems obvious. "Men are very simple creatures," said Walsh. "I'd be interested to see if he dates non-blondes."

3. Cross market appeal. He's got the perpetual scruff and brooding good looks of a New York City hunk; she's got the wavy light locks and porcelain skin of a corn-fed princess. By dating him, she gets to up her street cred, and he gets to say that he's in touch with all that space between Brooklyn and Hollywood.

4. Caffeine co-dependency. The couple's recent outings have centered on coffee. On Thanksgiving, Swift and Gyllenhaal reportedly hit up Brooklyn's Gorilla Coffee (near where Jake's sister, Maggie, lives) for speciality lattes made with Vermont maple syrup. On Saturday, they grabbed cups of the stuff at Nashville's Fido cafe. Maybe a shared love of Joe has led to an inseparable, if at times jittery, bond.

5. They actually, uh, like each other. It's easy to be cynical about a couple who comes from a class of people who often gives the same care to relationships as it does to Facebook status updates, but in Swift and Gyllenhaal's case, their romance could be the real thing.

"Sure, there's a 10 year age difference and the last woman Jake dated was a divorcee with two kids, but they're two very attractive people, very successful, and very famous -- this is not unheard of," said Julie Dam, assistant managing editor at People magazine. "They've spent time together in three different states and two different countries over the past month. From what we hear from sources and witnesses, they certainly seem to be enjoying each other's company."